The invention relates to an elastomer coupling for an electromechanical actuator with a drive part and a driven part, wherein either the drive part or the driven part has multiple webs that are arranged distributed about a rotational axis and extend radially outward and the other part has webs that are arranged on the inner side of a tubular body and extend radially inward, wherein a web extending radially inward and a web extending radially outward engage in each other and form a pocket in which an elastic molded body made from an elastomer is held.
An elastomer coupling is part of a roll stabilizer for a motor vehicle, wherein an active roll stabilizer can be installed on a front axle or on a rear axle of a motor vehicle. An electromechanical roll stabilizer comprises an electric motor, a control unit, a multi-step planetary gear, and an elastomer coupling that is part of an elastomer decoupling unit (EKE) and decouples the actuator from effects due to unevenness in the roadway during straightaway driving. Small amounts of torsion between torsion bars are absorbed by molded bodies made from an elastomer.
A roll stabilizer with an elastomer coupling is known from EP 2 213 489 A1. A drive part is here formed as an inner star body and a driven part is formed as an outer star body; a molded body made from an elastomer is held between the inner and outer webs that engage with each other. In this way, a certain desired profile of the torque over the rotational angle between the drive part and the driven part or between the two torsion bars of the roll stabilizer is produced. The active roll stabilizer exhibits high elasticity for small torques or torsional moments. Here, relative movements between the drive part and the driven part are possible through deformation of the molded body without transmitting a significant torque. Starting from a certain rotational angle, however, the transmitted torque increases progressively. For continued deformation of the molded body, a progressive increase in stiffness occurs. Thus, small rotations of the torsion bars of the stabilizer produced, e.g., by roadway unevenness, can be absorbed by the molded bodies, which increases driving comfort. When driving around a curve and also for different roadway unevenness between the right and the left side, the rolling motion of the vehicle can be reduced by active rotation of the two stabilizer halves by the roll stabilizer.
FIGS. 1-3 show components of an elastomer coupling developed by the applicant. FIG. 1 shows a drive part 1 with an inner star body 2 whose webs 3 have molded bodies 4, 5 molded on both sides. FIG. 2 shows a driven part 6 that is formed as an outer star body and has recesses adapted to the inner star body 2 and with a mirror-inverted shape. Clearances that allow the molded bodies 4, 5 to deform under loading are formed between the inner star body 2 and the outer star body. In the assembled state, the inner star body is inserted into the outer star body, wherein the elastomer coupling is formed that is suitable for transmitting a torsional moment.
FIG. 3 is an enlarged, section view of a web 2 of the inner star body shown in FIG. 1. The web 2 produced from a steel alloy has the molded bodies 4, 5 molded on both sides. Up to a certain rolling angle, the elastomer coupling has a soft response, that is, the slope in the stiffness characteristic curve is small. When a limit angle is reached, the molded body made from the elastomer is held completely in a recess between the inner star body and the outer star body and has an incompressible response. When this limit angle is exceeded, the elastomer coupling has a stiff response, that is, the stiffness characteristic curve has a large slope. This bilinear response of the elastomer coupling thus reduces, especially when driving on rough roadways, the number of necessary control actions of the roll stabilizer. Thus, the drive motor of the roll stabilizer is quasi decoupled from movements of the torsion bars due to the soft characteristic curve of the elastomer coupling.
For the functional principle of this known elastomer coupling, the elastomer material molded on the inner star body takes over the function of a spring that is loaded predominately into compression under torsional loading. Such an elastomer coupling can be understood as a parallel circuit, e.g., of five springs of equal stiffness that are loaded to the block position under loading.
For conventional elastomer couplings, the problem can occur that the elastic molded bodies that can be arranged either loosely in the pockets or can be molded on a web exhibit subsidence. This means that the elastic molded bodies produced from elastomer are permanently deformed after some time by the loads that occur, so that play can occur between the drive part and the driven part, more precisely between the inner star body and the outer star body. In this state, if there is no pretensioning between the two components of the elastomer coupling that can move relative to each other, undesired acoustic emissions can be produced.